IG window unit having triple silver coating and dielectric coating on opposite sides of glass substrate

ABSTRACT

An insulating glass (IG) window unit including first and second glass substrates that are spaced apart from each other. At least one of the glass substrate has a triple silver low-emissivity (low-E) coating on one major side thereof, and a dielectric coating for improving angular stability on the other major side thereof.

This application is a continuation of application Ser. No. 15/917,909,filed Mar. 12, 2018, which is based on Provisional Application Ser. No.62/469,556, filed Mar. 10, 2017, the entire disclosures of which arehereby incorporated herein by reference in its entireties.

This invention relates to an insulating glass (IG) window unit includingfirst and second glass substrates that are spaced apart from each other.At least one of the glass substrate has a triple silver low-emissivity(low-E) coating on one major side thereof, and a dielectric coating forimproving angular stability on the other major side thereof.

BACKGROUND AND SUMMARY OF THE INVENTION

Low solar factor (SF) and solar heat gain coefficient (SHGC) values aredesired in some applications, particularly in warm weather climates.Solar factor (SF), calculated in accordance with EN standard 410,relates to a ratio between the total energy entering a room or the likethrough a glazing and the incident solar energy. Thus, it will beappreciated that lower SF values are indicative of good solar protectionagainst undesirable heating of rooms or the like protected bywindows/glazings. A low SF value is indicative of a coated article(e.g., IG window unit) that is capable of keeping a room fairly cool insummertime months during hot ambient conditions. Thus, low SF values aresometimes desirable in hot environments. High light-to-solar gain (LSG)values are also desirable. LSG is calculated as T_(vis)/SHGC. The higherthe LSG value, the more visible light that is transmitted and the lessamount of heat that is transmitted by the coated article. While low SFand SHGC values, and high LSG values, are sometimes desirable for coatedarticles such as IG window units and/or monolithic windows, theachievement of such values may come at the expense of sacrificingcoloration and/or reflectivity values. In particular, conventionalattempts to achieve low SHGC values have often resulted in undesirablylow LSG values and/or undesirable visible coloration of the coating. Itis often desirable, but difficult, to achieve a combination ofacceptable visible transmission (TY or T_(vis)), desirable glass sidereflective coloration (e.g., desirable a* and b* glass side reflectivecolor values), low SHGC, desirably low film side visible reflectance,and high LSG for a coated article in window applications, especially ifit desired to use a glass substrate that is not deeply tinted.

SF (G-Factor; EN410-673 2011) and SHGC (NFRC-2001) values are calculatedfrom the full spectrum (T_(vis), Rg and Rf) and are typically measuredwith a spectrophotometer such as a Perkin Elmer 1050. The SFmeasurements are done on monolithic coated glass, and the calculatedvalues can be applied to monolithic, IG and laminated applications.

It would be desirable according to example embodiments of this inventionfor a coating to be designed so as to have a combination of acceptablevisible transmission (TY or T_(vis)), low emittance/emissivity, lowSHGC, and high LSG for a coated article in window applications.

In certain embodiments of this invention there is provided an insulatingglass (IG) widow unit comprising: first and second glass substrates;wherein the first glass substrates supports a low-E coating and adielectric coating on opposite major surfaces thereof; wherein the low-Ecoating comprises first, second, and third infrared (IR) reflectinglayers comprising silver separated by at least dielectric layers;wherein the dielectric coating comprises a plurality of alternating highindex and low index layers that contact each other; and wherein thelow-E coating and the dielectric coating are configured so that the IGwindow unit has an LSG value of at least 2.0, and a ΔC value of nogreater than 3.0 as viewed from an exterior of a building in which theIG window unit is to be mounted across a range of angles of at least 85degrees.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a coated article according to anexample embodiment of this invention.

FIG. 2 is a cross sectional view showing the coated article of FIG. 1provided in an IG window unit according to example embodiments of thisinvention (on surface two of an IG window unit).

FIG. 3 illustrates graphs according to example embodiments of thisinvention plotting wavelength (nm) versus optical features includingtransmission (T) and Reflection (R).

FIG. 4 is an angle versus glass side reflective a*, b* color value graphillustrating very low variation in glass side reflective a* and b* colorvalues across a wide range of angles according to an example embodimentof this invention.

DETAILED DESCRIPTION OF EXAMPLES OF THE INVENTION

Referring now more particularly to the accompanying drawings in whichlike reference numerals indicate like parts throughout the severalviews/embodiments.

Low-emissivity coating glass is widely used in commercial andresidential buildings, including in IG window units. Window color isimportant for people in selection of windows, and window color variationfrom a large building could be an intolerance issue for architectures.The color of a window coating from the first story to the top story of atall building can be varied due to the reflection at different angles.Thus, herein we resolve the angular color variation issue for windowglass coating, by reducing variation in color across a large range ofviewing angles.

This angular color issue is a trade off with respect to LSG value fortriple silver low-E coatings. In particular, in general the higher theLSG value, the worse the angular color issues. Thus, heretofore it hasnot been possible to combine a high LSG value with a reduced variationin color across a wide range of viewing angles.

The parameter ΔC may be used for quantitatively calculating variation ofcolor across viewing angle,ΔC=√{square root over ((a−a _(o))²+(b−b _(o))²)}

Note that a, b and a_(o), b_(o) are two color values (a*, b* colorvalues, which may be transmissive, glass side/exterior reflective, orfilm side/interior reflective) at different viewing angles. Forinstance, a maxim ΔC cross 0-90 degrees for example may be used for ameasure of how much color varied cross this angle range. The low-Ecoating is widely used in the window coating, and the angular color isan issue to nearly most of triple silver with high LSG at the highbuildings. Example triple silver low-E coatings are shown in FIG. 1, andin the provisional application upon which this application is based. Inan IG window unit, an optimized angular color ΔC is typically very largeas explained herein, typically increasing as LSG increases.

Normally, human eyes can distinguish ΔC>>3 easily. However, if ΔC<2 thenit is hard to human eyes to easily tell the difference. Thus, it isdesirable herein to combine a triple silver in a window so as to haveboth a high LSG value (e.g., at least 2.0, more preferably at least 2.2,and most preferably at least 2.3) and a ΔC value of no greater than 4.0,more preferably no greater than 3.0, more preferably no greater than2.5, and most preferably no greater than 2.0, and most preferably nogreater than 1.5, especially in connection with glass side/exteriorreflective color values a* and b*, across a wide range of angles such as60 degrees, or even 85 or 90 degrees.

In example embodiments of this invention, we found a solution and way toachieve the desirable features by providing a second glass side coatingin an IG window unit. An insulating glass (IG) window unit includesfirst and second glass substrates that are spaced apart from each other.At least one of the glass substrates 1 has a triple silverlow-emissivity (low-E) coating 30 on one major side thereof, and adielectric coating 31 for improving angular stability on the other majorside thereof.

The left side graph in FIG. 3 is a plot for a typical triple silvercoating 30, without any additional dielectric coating 31 (bad angularcolor variation ΔC˜14). The middle graph in FIG. 3 is a plot for theadditional dielectric coating 31 alone on the glass substrate with highvisible transmission but very low near IR transmission (800˜1700 nm).And the right-hand graph in FIG. 3 is a plot for the combination oftriple silver low-E coating 30 and additional dielectric coating 31 onopposite sides of the glass substrate. When combining the two coatings30 and 31 on opposite sides of the glass substrate 1, it wassurprisingly found that ΔC dropped significantly down to less than 1.5,as evidenced by FIG. 4 which illustrates the very low variation in glassside reflective a* and b* color values across a wide range of angleswhen both coatings 30 and 31 were present.

In example embodiments of this invention, dielectric angular reductioncoating 31 may be made up of alternating high index (e.g., TiO₂ or Nboxide) and low index (e.g., SiO₂) layers, with example being fifty-twosuch layers in alternating fashion to make up coating 31 in order toachieve high transparency in the visible spectra (400 nm˜700 nm), andlow transparency in the near IR spectra (800 nm˜1700 nm), so as tocontrol the solar energy to achieve high LSG values (e.g., 2.34 withthis coating in the FIG. 1-4 embodiment). The high index layers ofcoating 31 may have a refractive index (n, at 550 nm) of from about 2.2to 2.5, and the low index layers of coating 31 may have a refractiveindex of from about 1.2 to 1.6, more preferably from about 1.45 to 1.58,in certain example embodiments of this invention. Dielectric angularreduction coating 31 may be made by various methods, such as thermalevaporation, magnetron sputtering, e-beam sputtering, sol-gel,multilayer polymer, or the like.

Thus, in example embodiments of this invention, we developed a newtechnique that solves the triple silver angular color issue via the useof special dielectric angular reduction coating 31 on the other side ofthe glass substrate 1 from the triple silver low-E coating 30, so as toprovide a low ΔC such as no greater than 1.5, across a wide range ofangles such as 60 degrees, or even 85 or 90 degrees.

Example embodiments of this invention relate to a coated articleincluding a low emissivity (low-E) coating 30 and dielectric angularreduction coating 31 supported on opposite major sides of a glasssubstrate 1. Coating 30 may be sputter-deposited. The coated article maybe heat treated (e.g., thermally tempered, heat bent and/or heatstrengthened).

FIG. 1 is a side cross sectional view of a coated article according toan example non-limiting embodiment of this invention, where the low-Ecoating 30 has three silver-based IR reflecting layers 9, 19 and 29. Thecoated article includes substrate 1 (e.g., clear, green, bronze, orblue-green glass substrate from about 1.0 to 10.0 mm thick, morepreferably from about 1.0 mm to 8.0 mm thick, e.g., about 6 mm thick),and coating (or layer system) 30 provided on the substrate 1 eitherdirectly or indirectly. The coating (or layer system) 30 includes:bottom silicon nitride inclusive transparent dielectric layer 3 whichmay be Si₃N₄, of the Si-rich type for haze reduction, or of any othersuitable stoichiometry in different embodiments of this invention,optional dielectric layer 5 of a material such as an oxide of titanium,first lower contact layer 7 (which contacts IR reflecting layer 9),first conductive and preferably metallic or substantially metallicinfrared (IR) reflecting layer 9, first upper contact layer 11 (whichcontacts layer 9), transparent dielectric layer 14 of or including zincstannate over and contacting the contact layer 11, optional transparentdielectric silicon nitride inclusive layer 15, second lower contactlayer 17 (which contacts IR reflecting layer 19), second conductive andpreferably metallic or substantially metallic IR reflecting layer 19,second upper contact layer 21 (which contacts layer 19), transparentdielectric layer 23, and optional transparent silicon nitride inclusivedielectric layer 25. The coating 30 further includes transparentdielectric lower contact layer 27 of or including zinc oxide, optionaltransparent third lower contact layer 28 of or including NiCr, NiCrOx orthe like, third conductive and preferably metallic or substantiallymetallic IR reflecting layer 29, third upper contact layer 31 (whichcontacts layer 29), transparent dielectric layer 33, and transparentsilicon nitride inclusive dielectric layer 35. It is also possible toreplace tin oxide layer 33 or any other tin oxide layer (e.g., 23) witha zinc stannate layer similar to layer 14 so that the zinc stannatelayer would be over and directly contacting contact layer 31 forinstance. It is also possible to replace the layer 5 with a layer of orincluding zinc stannate or the like.

In monolithic instances, the coated article includes only one glasssubstrate 1 as illustrated in FIG. 1. However, monolithic coatedarticles herein may be used in devices such as laminated vehiclewindshields, IG window units, and the like. As for IG window units, anIG window unit may include at least two spaced apart glass substrates.An example IG window unit is illustrated and described, for example, inU.S. Patent Document No. 2004/0005467, the disclosure of which is herebyincorporated herein by reference. FIG. 2 shows an example IG window unitincluding the coated glass substrate 1 shown in FIG. 1 coupled toanother glass substrate 2 via spacer(s), sealant(s) 40 or the like, witha gap 50 being defined therebetween. This gap 50 between the substratesin IG window unit embodiments may in certain instances be filled with agas such as argon (Ar), or a mixture of Ar gas and air. An example IGunit may comprise a pair of spaced apart clear glass substrates 1 and 2each about 3-8 mm thick (e.g., about 6 mm thick), one of which is coatedwith a coating 30 herein in certain example instances, where the gap 50between the substrates may be from about 5 to 30 mm, more preferablyfrom about 10 to 20 mm, and most preferably about 16 mm. In certainexample instances, the low-E coating 30 may be provided on the interiorsurface of either substrate facing the gap. Either substrate 1 orsubstrate 2 may be the outermost substrate of the IG window unit at thebuilding exterior (e.g., in FIG. 2 the substrate 1 is the substrateclosest to the building exterior, and the low-E coating 30 is providedon surface #2 of the IG window unit). In preferred embodiments of thisinvention, the coating 30 is provided on surface #2 of the IG windowunit, and coating 31 may be provided on surface #1, as shown in FIG. 2.

Dielectric layers 3, 15, 25 and/or 35 may be of or include siliconnitride in certain embodiments of this invention. The silicon nitride ofthese layers may be of the stoichiometric type (i.e., Si₃N₄), oralternatively of the Si-rich type in different embodiments of thisinvention.

Infrared (IR) reflecting layers 9, 19 and 29 are preferablysubstantially or entirely metallic and/or conductive, and may compriseor consist essentially of silver (Ag), gold, or any other suitable IRreflecting material. IR reflecting layers 9, 19 and 29 help allow thecoating to have low-E and/or good solar control characteristics. The IRreflecting layers may, however, be slightly oxidized in certainembodiments of this invention.

The upper contact layers 11, 21 and 31 (and possibly lower contact layer28) may be of or include nickel (Ni) oxide, chromium/chrome (Cr) oxide,or a nickel alloy oxide such as nickel chrome oxide (NiCrO_(x)),NiCrMoO_(x), or other suitable material(s) such as Ti or an oxide of Ti,in certain example embodiments of this invention.

Transparent dielectric layers 23 and 33 may be of or include tin oxidein certain example embodiments of this invention. However, it may bedoped with certain other materials in other example embodiments, such aswith Al or Zn in certain example alternative embodiments.

Lower contact or seed layers 7, 17 and/or 27), in certain embodiments ofthis invention are of or include zinc oxide (e.g., ZnO). The zinc oxideof these layers may contain other materials as well such as Al (e.g., toform ZnAlO_(x)). For example, in certain example embodiments of thisinvention, one or more of zinc oxide layers may be doped with from about1 to 10% Al, more preferably from about 1 to 5% Al, and most preferablyabout 1 to 4% Al.

Other layer(s) below or above the illustrated coating may also beprovided. Thus, while the layer system or coating is “on” or “supportedby” substrate 1 (directly or indirectly), other layer(s) may be providedtherebetween. Thus, for example, the coating of FIG. 1 may be considered“on” and “supported by” the substrate 1 even if other layer(s) areprovided between layer 3 and substrate 1. Moreover, certain layers ofthe illustrated coating may be removed in certain embodiments, whileothers may be added between the various layers or the various layer(s)may be split with other layer(s) added between the split sections inother embodiments of this invention without departing from the overallspirit of certain embodiments of this invention.

While various thicknesses and materials may be used in layers indifferent embodiments of this invention, example thicknesses andmaterials for the respective layers of coating 30 on the glass substrate1 in the FIG. 1 embodiment are as follows, from the glass substrateoutwardly:

Example Materials/Thicknesses Layer Glass Preferred More (1-10 mm thick)Range ({acute over (Å)}) Preferred ({acute over (Å)}) Example (Å)Si_(x)N_(y) (layer 3) 40-600 Å 100-300 Å 136 Å TiO_(x) (layer 5) 7-150 Å7-50 Å 10 Å ZnAlO_(x) (layer 7) 10-300 {acute over (Å)} 60-140 {acuteover (Å)} 90 Å Ag (layer 9) 50-250 {acute over (Å)} 80-120 {acute over(Å)} 109 Å NiCrO_(x) (layer 11) 10-100 {acute over (Å)} 20-40 {acuteover (Å)} 30 Å ZnSnO (layer 14) 200-800 Å 350-600 Å 435 Å Si_(x)N_(y)(layer 15) 50-350 {acute over (Å)} 80-200 {acute over (Å)} 130 ÅZnAlO_(x) (layer 17) 80-300 {acute over (Å)} 170-250 {acute over (Å)}220 Å Ag (layer 19) 60-160 {acute over (Å)} 90-130 {acute over (Å)} 110Å NiCrO_(x) (layer 21) 10-100 {acute over (Å)} 20-40 {acute over (Å)} 30Å SnO₂ (layer 23) 50-750 Å 150-300 Å 220 Å Si₃N₄ (layer 25) 10-750{acute over (Å)} 100-170 {acute over (Å)} 130 Å ZnAlO_(x) (layer 27)50-300 {acute over (Å)} 190-260 {acute over (Å)} 238 Å NiCrO_(x) (layer28) 7-40 {acute over (Å)} 7-20 {acute over (Å)} 10 Å Ag (layer 29)50-250 {acute over (Å)} 120-135 {acute over (Å)} 120 Å NiCrO_(x) (layer31) 10-100 {acute over (Å)} 20-40 {acute over (Å)} 30 Å SnO₂ (layer 33)0-750 Å 50-120 Å 75 Å Si₃N₄ (layer 35) 10-750 {acute over (Å)} 100-250{acute over (Å)} 201 Å

In certain example embodiments of this invention, coated articlesaccording to the FIG. 1 embodiment may have the following optical andsolar characteristics when measured monolithically before and/or afteroptional HT. The sheet resistances (R_(s)) herein take into account allIR reflecting layers (e.g., silver layers 9, 19, 29).

Optical/Solar Characteristics Characteristic General More Preferred MostPreferred R_(s) (ohms/sq.): <=3.0  <=2.5  <=2.0 or <=1.6 or <=1.4 E_(n):<=0.07 <=0.04 <=0.03 T_(vis) (Ill. C 2°): >=40% >=50% >=60%

In certain embodiments of this invention there is provided an insulatingglass (IG) widow unit comprising: first and second glass substrates;wherein the first glass substrates supports a low-E coating and adielectric coating on opposite major surfaces thereof; wherein the low-Ecoating comprises first, second, and third infrared (IR) reflectinglayers comprising silver separated by at least dielectric layers;wherein the dielectric coating comprises a plurality of alternating highindex and low index layers that contact each other; and wherein thelow-E coating and the dielectric coating are configured so that the IGwindow unit has an LSG value of at least 2.0, and a ΔC value of nogreater than 3.0 as viewed from an exterior of a building in which theIG window unit is to be mounted across a range of angles of at least 85degrees.

In the IG window unit of the immediately preceding paragraph, whereinthe low-E coating and the dielectric coating may be configured so thatthe IG window unit has an LSG value of at least 2.2, and/or a ΔC valueof no greater than 2.5 as viewed from an exterior of a building in whichthe IG window unit is to be mounted across a range of angles of at least85 degrees.

In the IG window unit of any of the preceding two paragraphs, the low-Ecoating and the dielectric coating may be configured so that the IGwindow unit has an LSG value of at least 2.3, and/or a ΔC value of nogreater than 2.0 as viewed from an exterior of a building in which theIG window unit is to be mounted across a range of angles of at least 85degrees.

In the IG window unit of any of the preceding three paragraphs, thelow-E coating and the dielectric coating may be configured so that theIG window unit has an LSG value of at least 2.3, and/or a ΔC value of nogreater than 1.5 as viewed from an exterior of a building in which theIG window unit is to be mounted across a range of angles of at least 85degrees.

In the IG window unit of any of the preceding four paragraphs, the low-Ecoating may have a sheet resistance (R_(s)) of no greater than 2.0ohms/square.

In the IG window unit of any of the preceding five paragraphs, the highindex layers may comprise an oxide of titanium or niobium.

In the IG window unit of any of the preceding six paragraphs, the lowindex layers may comprise an oxide of silicon.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

The invention claimed is:
 1. An insulating glass (IG) widow unitcomprising: first and second glass substrates; wherein the first glasssubstrate supports a low-E coating and an angular reduction dielectriccoating on respective opposite major surfaces thereof, respectively;wherein the low-E coating comprises first, second, and third infrared(IR) reflecting layers comprising silver, wherein at least a firstdielectric layer of the low-E coating is provided between at least thefirst and second IR reflecting layers comprising silver, and at least asecond dielectric layer of the low-E coating is provided between atleast the second and third IR reflecting layers comprising silver;wherein the angular reduction dielectric coating, which is on a side ofthe first glass substrate opposite the low-E coating, comprises aplurality of high index and low index layers; and wherein the low-Ecoating and the angular reduction dielectric coating are configured sothat the IG window unit has a ΔC value of no greater than 3.0 as viewedfrom an exterior of a building in which the IG window unit is to bemounted across a range of angles of at least 85 degrees from a normalviewing angle which is perpendicular to the IG window unit, and whereinΔC is defined asΔC=[(a−a _(o))²+[(b−b _(o))²]^(1/2) where “a” is an a* color value atthe normal viewing angle, and “a_(o)” is an a* color viewing angle atthe off-axis viewing angle, “b” is a b* color value at the normalviewing angle, and “b_(o)” is a b* color viewing angle at the off-axisviewing angle.
 2. The IG window unit of claim 1, wherein the low-Ecoating and the dielectric coating are configured so that the IG windowunit has an LSG value of at least 2.2, and a ΔC value of no greater than2 5 as viewed from an exterior of a building in which the IG window unitis to be mounted across a range of angles of at least 85 degrees.
 3. TheIG window unit of claim 1, wherein the low-E coating and the dielectriccoating are configured so that the IG window unit has an LSG value of atleast 2.3, and a ΔC value of no greater than 2 0 as viewed from anexterior of a building in which the IG window unit is to be mountedacross a range of angles of at least 85 degrees.
 4. The IG window unitof claim 1, wherein the low-E coating and the dielectric coating areconfigured so that the IG window unit has an LSG value of at least 2.3,and a ΔC value of no greater than 1 5 as viewed from an exterior of abuilding in which the IG window unit is to be mounted across a range ofangles of at least 85 degrees.
 5. The IG window unit of claim 1, whereinthe low-E coating has a sheet resistance (R_(s)) of no greater than 2.0ohms/square.
 6. The IG window unit of claim 1, wherein the high indexlayers comprise an oxide of titanium.
 7. The IG window unit of claim 1,wherein the high index layers comprise an oxide of niobium.
 8. The IGwindow unit of claim 1, wherein the low index layers comprise an oxideof silicon.
 9. An insulating glass (IG) widow unit comprising: first andsecond substrates; wherein the first substrate supports a low-E coatingand an angular reduction dielectric coating on respective opposite majorsurfaces thereof, respectively; wherein the low-E coating comprisesfirst, second, and third infrared (IR) reflecting layers, wherein atleast a first dielectric layer of the low-E coating is provided betweenat least the first and second IR reflecting layers, and at least asecond dielectric layer of the low-E coating is provided between atleast the second and third IR reflecting layers; wherein the angularreduction dielectric coating, which is on a side of the first glasssubstrate opposite the low-E coating, comprises at least one high indexlayer and at least one low index layer; and wherein the low-E coatingand the angular reduction dielectric coating are configured so that theIG window unit has a ΔC value of no greater than 3.0 as viewed from anexterior of a building in which the IG window unit is to be mountedacross a range of angles of at least 85 degrees from a normal viewingangle which is perpendicular to the IG window unit, and wherein ΔC isdefined asΔC=[(a−a _(o))²+[(b−b _(o))²]^(1/2) where “a” is an a* color value atthe normal viewing angle, and “a_(o)” is an a* color viewing angle atthe off-axis viewing angle, “b” is a b* color value at the normalviewing angle, and “b_(o)” is a b* color viewing angle at the off-axisviewing angle.